Skyline clamp for logging carriage

ABSTRACT

The carriage is moved back and forth on a skyline by which drums on a yarder at one end of the skyline. The carriage contains a three-section cable drum having individual sections for a main line, a haulback line and a hoisting line. A hydraulic brake in the carriage operates on the three-section drum and a hydraulic clamp operates on the skyline. When the carriage drum brake is set and the skyline clamp released, the yarder winch drums pull the carriage out by winding in the haulback line and slacking off the main line. The yarder winch drums pull the carriage in by winding in the main line and slacking off the haulback line. When a turn of logs is to be lifted by the carriage for travel back to the yarder, the skyline clamp is set and the carriage drum brake released. The logs are lifted by causing the yarder main line winch to pull in the main line while the haulback line is slacked at the yarder. The skyline clamp and drum brake in the carriage are actuated by a special leak-proof hydraulic system. A hydrostatic transformer provides a high pressure source of hydraulic fluid for the clamp. The hydraulic system is supplied by a bi-rotational pump operated by rotation of the carriage cable drum and pressurized oil is stored in an accumulator when the pump is not operating. Valves for actuating and releasing the brake and clamp are radio controlled by an operator at the yarder. To facilitate putting the carriage on the skyline and removing it from the skyline, the skyline clamp is made accessible by a hinged frame so that the skyline does not have to be threaded lengthwise through the clamp shoes. A movable clamp shoe extending substantially the length of the carriage is actuated by a plurality of hydraulic cylinders spaced along the shoe to provide quick and positive clamp and release movements and avoid sliding wear on the skyline cable.

United States Patent 1191 Junes et al.

[ June 28, 1974 SKYLINE CLAMP FOR LOGGING CARRIAGE [76] Inventors:Norman E. Junes, 3 Box 148,

Astoria, Oreg. 97103; William R. Stanyer, 1715 Franklin, Seaside, Oreg.97138 [22] Filed: Aug. 17, 1973 [21] Appl. No.: 389,369

Related U.S. Application Data [62] Division of $81. No. 153,984, JuneI7, 1971.

[52] U.S. Cl. 212/99 [51] Int. Cl. B66c 21/00 [58] Field of Search212/99, 103, 107, 111, 212/24, 89, 96, I15, 97, 98; 254/148 [56]References Cited UNITED STATES PATENTS 3,083,839 4/1963 Mclntyre 212/98X Primary Examiner-Stanley H. Tollberg Attorney, Agent, or Firm-Lee R.Schermerhorn [5 7] ABSTRACT The carriage is moved back and forth on askyline by which drums on a yarder at one end of the skyline. Thecarriage contains a three-section cable drum having individual sectionsfor a main line, a haulback line and a hoisting line. A hydraulic brakein the carriage operates on the three-section drum and a hydraulic clampoperates on the skyline. When the carriage drum brake is set and theskyline clamp released, the yarder winch drums pull the carriage out bywinding in the haulback line and slacking off the main line.

The skyline clamp and drum brake in the carriage are actuated by aspecial leak-proof hydraulic system. A hydrostatic transformer providesa high pressure source of hydraulic fluid for the clamp. The hydraulicsystem is supplied by a bi-rotational pump operated by rotation of thecarriage cable drum and pressurized oil is stored in an accumulator whenthe pump is not operating. Valves for actuating and releasing the brakeand clamp are radio controlled by an operator at the yarder. Tofacilitate putting the carriage on the skyline and removing itfrom theskyline, the skyline clamp is made accessible by a hinged frame so thatthe skyline does not have to be threaded lengthwise through the clampshoes. A movable clamp shoe extending substantially the length of thecarriage is actuated by a plurality of hydraulic cylinders spaced alongthe shoe to provide quick and positive clamp and release movements andavoid sliding wear on the skyline cable.

6 Claims, Drawing Figures a2 1 St m -r 32. 1 qJ H "85 (,0 33 20 15 33|35 "i 2 46 H5 zt'fi/ r it. 34 11 n 35 Vi t m I no PATENTEBmza 1914.

SHEET 1 (IF 6 a""""""" 7' s lll s ID V H:

PATENTEUJUNZB mm SHEU 5 OF 6 SKYLINE CLAMP FOR LOGGING CARRIAGECROSS-REFERENCE TO RELATED APPLICATION This application is a division ofour co-pending application Ser. No. 153,984 filed June 17, 1971, onSkyline Logging Carriage.

BACKGROUND OF THE INVENTION This invention relates to a skyline loggingcarriage for yarding logs in a logging operation.

Two primary objectives in a logging operation are speed and safety. Themain objections to previous logging carriages are that they have notbeen able to provide speed with safety. Earlier carriages were held inposition on the skyline by the main line if logging uphill or by thehaulback line if logging downhill. A failure of the holding line wouldallow the carriage to run free on the skyline by gravity, resulting in amajor disaster at the lower end of the line.

Attempts have been made to apply a brake on the skyline but thesecarriages have been unsuccessful because of excessive wear on theskyline and failure to hold positively. The existence of a skyline brakemade it difficult to put the carriage on the skyline and to remove itfrom the skyline whenever the skyline had to be shifted from one loggingarea to another. In some systems the cables become entangled and createa hazard as well as slowing up the work.

Attempts have been made to install a hoisting engine in the carriage butwithout success. An engine requires frequent service thereby entailingloss of time and adding to the care and maintenance of the system. Also,an internal combustion engine suitable for the purpose will not operatesatisfactorily in steeply inclined or upended position, or turned on itsside, as frequently occur in logging operations. When a carriage with anengine is dropped, a serious fire hazard is created during dryconditions.

Objects of the invention are, therefore, to provide an improved skylinecarriage, to provide a carriage that will speed up logging operationswithout sacrificing safety, to provide a carriage that is safe indownhill logging, to provide a carriage thatis more efficient overallthan existing carriages, to provide a carriage that is easy to put onthe skyline and take off from the skyline, to provide an improved highpressure hydraulic system, to provide an improved leak-proof multiplevalve unit, to provide an improved skyline clamp, to provide an improvedhydrostatic transformer, and to provide an improved bi-rotational pump.

SUMMARY OF THE INVENTION The present carriage has a three-section drumfor a main line, haulback line and hoisting line. The carriage is movedback and forth on a skyline by a yarder at one end of the skyline. Awinch drum on the yarder pulls the carriage in by winding in the mainline and a winch drum on the yarder pulls the carriage out by winding inthe haulback line. During these operations a hydraulic brake preventsrotation of the cable drum in the carriage.

When a turn of logs is to be raised up to the carriage or lowered fromthe carriage, a hydraulic clamp is ap plied to the skyline to hold thecarriage stationary and the drum brake is released. Then, when theyarder pulls are raised by the hoisting cable on the carriage cable drumand, when the yarder pays out the main line and winds in the haulbackline, the logs are lowered. An improved skyline clamp is provided whichdoes not damage the skyline.

A novel hydraulic system supplies the drum brake and skyline clamp underradio control. A novel hydrostatic transformer automatically intensifieshydraulic pressure three and one-half times for the skyline clamp. Anovel leak-proof multiple valve unit is provided'and a novel pump isoperated by rotation of the carriage cable drum in either direction.

Putting the carriage on the skyline and taking it off is facilitated bya novel arrangement of the skyline clamp. The skyline cable may bereadily inserted in and removed from the clamp jaws without threadingthe end of the skyline through the clamp mechanism.

The invention will be better understood and additional objects andadvantages will become apparent from the following description of thepreferred embodiment illustrated in the accompanying drawings. Variouschanges may be made in the details of construction and arrangement ofparts and certain features may be used without others. All suchmodifications within the scope of the appended claims are included inthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of alogging operation employing the invention;

FIG. 2 is an isometric exploded view with parts broken away, showing theskyline carriage in FIG. 1;

FIG. 3 is a view on the line 3-3 in FIG. 2;

FIG. 4 is a top plan view of the carriage with parts broken away;

FIG. 5 is a view on the line 5-5 in FIG. 4, showing the skyline clamp inoperative position;

FIG. 6 is a similar view, showing the overarm assembly raised and themovable clamp jaw partially removed;

FIG. 7 is a view on the line '77 in FIG. 4;

FIG. 8 is a view on the line 8-8 in FIG. 4;

FIG. 9 is a fragmentary sectional view of the carriage with parts inelevation, showing the cable drum and hydraulic pump;

FIG. 10 is an axial view of the pump in FIG. 9;

FIG. 11 is a view on the line 1l-l1 in FIG. 9;

FIG. 12 is an enlarged sectional view of a portion of FIG. 9, showingthe pump inlet valve;

FIG. 13 is a view on the line 13-13 in FIG. 9;

FIG. 14 is a view on the line 14-l4 in FIG. 9;

FIG. 15 is a view on the line 15--l5 in FIG. 9;

FIG. 16 is a view on the line 16-16 in FIG. 9;

FIG. 17 is a view on the line 17--l7 in FIG. 16;

FIG. 18 is a schematic diagram of the hydraulic and electric system;

FIG. 19 shows sectional views of the multiple valve unit and hydrostatictransformer including other parts of the hydraulic system in FIG. 1B;and

FIG. 20is a sectional view of a modification of the multiple valve unitin FIG. 17.

DESCRIPTION OF THE PREFERRED EMBODIMENT General Description and Mode ofOperation FIG. 1 illustrates a downhill logging operation which can becarried out safely with the present equipment but which cannot becarried out safely with any other known equipment. Carriage runs backand forth on an inclined skyline 11 to carry a turn of logs L down tothe yarder Y which is accessible to some means of transportation forhauling the logs away. The remote end of skyline 11 is supported inelevated position by a sheave on tail tree 12 with the end of theskyline anchored to a tail hold stump 13. Tail tree 12 is situated onconsiderably higher ground than the yarder Y whereby the skyline 11 issteeply inclined downhill from the tail tree to the yarder. Thistopographic feature has heretofore presented a great hazard in theoperation of conventional equipment.

Connected with carriage 10 are a main line 15, a haulback line 16 and ahoisting line 17 equipped with a choker hook 18. The yarder Y isequipped with a winch drum 20 to raise and tension the skyline 11, awinch drum 21 to pull in and pay out the main line 15, and a winch drum22 to pull in and pay out the haulback line 16. These lines are guidedto the yarder winch drums by sheaves on a mast 23 on the yarder.Haulback line 16 is returned to the yarder through pulley blocks 24 onstumps at one side of the working area so that the haulback line is keptclear of the working area and at a distance from skyline 1 1 and mainline 15 to prevent entanglement of the cables and danger to workmen.

Referring now to FIG. 2, carriage 10 is supported for travel on skylinel 1 by a pair of rider sheaves 30. Each rider sheave is mounted in abracket 31 having a transverse horizontal bore 32 on each side toreceive a pivot bolt 33. The pivot bolts 33 are mounted in holes 34 inthe opposite side plates 35 of the carriage frame. This provides ayieldable pivotal suspension in the event that the carriage or sheavesbump into a tree or other obstruction during travel on the skyline.

Side plates also support a stationary transverse shaft which carries athree-section cable drum 41. One end of the cable drum 41 is equippedwith a brake drum 42 having a brake band 43. The brake band may betightened to prevent rotation of cable drum 41 by a hydraulic brakecylinder 44.

Cable drum 41 has an end section 45 receiving and anchoring one end ofmain line 15, an opposite end section 46 receiving and anchoring one endof haulback line 16 and a center section 47 receiving and anchoring theupper end of hoisting line 17. The carriage has a lid or top plate 49carrying a skyline clamp generally designated by the numeral 50. Thebrake 43 and clamp 50 are controlled by radio as will presently beexplained.

As shown in FIGS. 9, l6 and 17, an arcuate plate 51 of short radiuscurvature is welded into an opening 52 in winding drum plate 53. Plate51 has an axial keyhole slot with a wide portion 54 to receive the cableand ferrule 55 and a narrow portion 56 to pass the cable into acircumferential slot 57 which anchors the ferrule. In case the drumrotation should overrun the length of the cable, the cable will readilyswing to the opposite end of slot 57 and start winding up again withoutkinking the cable.

FIG. 17 shows the normal position of cable 17 and ferrule 55 in fulllines. The step of inserting the ferrule in wide slot portion 54 isshown in broken lines and the reverse winding position of the cable andferrule is also shown in broken lines. The other two cables 15 and 16are anchored in the same manner in drum sections 45 and 46. Cable 16 isguided by the fairlead 58 in FIG. 2.

When it is desired to pull the carriage 10 out toward tail tree 12,cable drum brake 43 is set and skyline clamp 50 is released..Thecarriage is pulled out by pulling in haulback line 16 by means of yarderhaulback winch drum 22 and paying out main line 15 from yarder main linewinch drum 21. When the carriage has reached a point where it is desiredto pick up a turn of logs, the skyline clamp 50 is set and cable drumbrake 43 is released. Then, by pulling in more haulback line 16 onyarder winch drum 22 and paying out more main line 15 from yarder winchdrum 21, the carriage cable drum 41 is rotated in a clockwise directionin FIG. 2 to lower the hoisting cable 17 and choker hook 18.

When the choker hook 18 on hoisting cable 17 has been secured to a turnof logs, the logs are raised by rotating carriage cable drum 41counterclockwise with clamp 50 applied on skyline 11. This isaccomplished by pulling in main line 15 on yarder winch drum 21 andpaying out haulback line 16 from yarder winch drum 22. When the logshave been raised sufficiently as shown in FIG. 1, carriage drum brake 43is applied to prevent rotation of drum 41 and skyline clamp 50 isreleased.

In the downhill logging operation in FIG. 1, the carriage 10 with itsturn of logs will travel back to the yarder by gravity, yarder haulbackwinch drum 22 paying out haulback line 16 at a rate to control the speedof the carriage. At the same time, slack in main line 15 is taken up onyarder main line winch drum 21. In logging on the level or uphill, thecarriage is pulled back to the yarder by main line winch drum 21.

When the carriage reaches its unloading point adjacent the yarder, indownhill logging as shown in FIG. 1, its movement is arrested by brakingthe yarder haulback winch drum 22 until the carriage comes to rest. Thenskyline clamp 50 is set and carriage drum brake 43 is released. Payingout main line 15 from yarder main line winch drum 21 allows carriagedrum 41 to rotate clockwise in FIG. 2 and lower the turn of logs onhoisting line 17. Thus, the movements of carriage 10 on skyline 11 andthe raising and lowering of hoisting line 17 are controlled throughyarder winch drums 21 and 22 and drum brake 43 and skyline clamp 50 onthe carriage.

Skyline Clamp Referring now to FIGS. 2 and 4 to 8, carriage lid plate 49is securely fastened to the carriage by bolts and dowels. The lid plateis removable as shown in FIG. 2 for access to the mechanism inside thecarriage. As best shown in FIG. 6, the stationary clamp jaw 60 comprisesa long angle iron equipped with a similar angle iron liner 61 whichengages the skyline cable 11. These parts are welded to lid plate 49 andalso to an inclined thrust plate 62. Welded on top of jaw 60 is ahorizontal pivot plate 63 having a rounded pivot edge or tongue 65. Theparts 60, 61, 62 extend approximately the entire length of lid plate 49.There are a number of the pivot plates 63, each of relatively shortlength as will presently be explained.

Movable clamp jaw 66 comprises an angle iron welded to a thrust bar 67and equipped with an angle iron liner 68. These parts extendapproximately the full length of lid plate 49. Clamping pressure isapplied at intervals along thrust bar 67 by a plurality of hydrauliccylinder and piston units 70, 71. Each unit nestles loosely in a hole 72in lid plate 49 with piston 71 engaging an edge of thrust bar 67 asshown in FIG. 4. Holes 72 are rectangular and of less-width thancylinders 70 whereby the side edges of the holes support the cylinderand piston units with the lower sides thereof projecting through plate49.

Movable jaw 66 and clamp cylinders 70 are secured in assembled relationby pairs of overarms 73 as shown in FIGS. 4 and 5. The arms 73 of eachpair are spaced apart the same distance as the width of the underlyinghole 72 to hold the cylinders loosely in the holes. Each pair ofoverarms 73 is welded at one end to a hinge pin 75 which is mounted forrotation in hinge ears 76 on lid plate 49. A block 77 spans the overarms73 and overlies thrust bar 67 to prevent uplift of jaw 66 when theoverarms are in closed position as shown in FIG. 5. Clamp cylinders 70have flathead ends which abut against hinge pins 75 and the ends ofholes 72 to sustain the thrust reaction under clamping pressure.

The swinging ends of overarms 73 are connected with short oval bushings79 which contain a round bar 80 extending approximately the length oflid plate 49. Bar 80 contains a longitudinal groove 81 to fit the tongue65 as shown in FIG. 5. Lever arms 82 are provided for rotating bar 80clockwise as shown in broken lines in FIG. 5 to disengage groove 81 fromthe tongue 65 so that all the overarms 73 may be swung clockwise inunison on their pivot bolts 75 as shown in FIG. 6. Thus, tongue 65 andgroove 81 form a quick releasable toggle joint for holding the overarms73 securely in operative position in FIG. 5. The overarms swing downinto the plane of pivot plates 63 in open intervals between the pivotplates.

Referring now to FIG. 4, the overarms 73 are secured in operativeposition by a rod 85 extending approximately the length of lid plate 49which is inserted through a series of apertured ears 86 upstanding onthrust plate 62. Rod 85 also extends through an opening 87 (FIG. 6) inthe end of each lever 82. As shown in FIGS. 4 and 5, a lock arm 90having an opening 91 is welded on one end of rod 85. In locked positionthe end of arm 90 is disposed between the end lever arm 82 and anupstanding ear 92 on thrust plate 62. This end lever arm 82 has anopening 93 (FIG. 6) to register with the opening 91 whereby a pin 94inserted through openings91 and 93 secures rod 85 and lock arm 90 inlocked position.

Movable jaw 66 is retracted by retractor cylinder and piston units 95,96 in FIGS. 4 and 7. There is a pair of these retractor units, eachcylinder being flexibly mounted in lid plate 49 by a bolt 97 welded atone end to the under side of the cylinder. Bolt 97 extends through alarge hole 98 in lid plate 49 and cylinder 95 is supported. at theproper height above the plate by upper and lower stacks of resilientrubber washers 99 clamped against opposite sides of the plate by a nut100. Hydraulic fluid is supplied to cylinder 95 by a nipple welded onthe under side of the cylinder and extending through an enlarged hole106 in lid plate 49.

The head end of cylinder 95 is rounded to fit a rounded depression 107in an abutment block 108 welded on lid plate 49. In a similar manner,the outer end of piston 96 is rounded to fit a rounded depression 109 inthe cross member of a U-shaped yoke or stirrup 110, the ends of whichare welded to the thrust bar 67.

Extension of pistons 96 in the two retractor cylinders 95 act throughthe two yokes 110 to retract thrust bar 67 and movable clamp jaw 66 tothe right in FIG. 7.

Thus, the series of clamp cylinder and piston units 70, 71 and the pairof retractor cylinder and piston units 95, 96 are all loosely andflexibly mounted to ad just themselves to the position of movable clampjaw 66. Any slight endwise movement: of clamp jaw 66 does not imposeside loading on the pistons.

From the foregoing description it will be apparent that movable clampjaw 66 includes as an integral part thereof, in addition to its liner68,. the thrust bar 67.and the two retractor yokes 110. This clamp jawunit is bodily removable by opening the overarm assembly 73 as shown inFIG. 6. There is sufficient clearance between thrust bar 67 and abutmentblock 108 in FIG. 7 to permit yoke 110 to be pulled manually farther tothe right after piston 96 is fully extended in order to disengagedepression 109 from the end of the piston.

Complete removal of the movable jaw unit facilitates various operations,such as mounting carriage on the skyline and removing it from theskyline, renewing the clamp jaw liners 61 and 68 when necessary, orchanging the liners to fit a different size of skyline cable 11. Clampcylinders 70 are also removable by merely disconnecting their hydraulicfittings and retractor cylinders 95 are removable by detaching thehydraulic connections and unscrewing nuts 100. These hydraulicconnections comprise clamp cylinder manifold and retractor cylindermanifold 116 in FIGS. 2 and 5.

End thrust means are provided for preventing longitudinal movement ofmovable clamp jaw 16. The opposite ends of movable jaw 66 and thrust bar67 in FIG. 2 bear against abutment blocks 111 as further illustrated inFIGS. 4, 5, 6 and 8. Each abutment block 111 is welded to lid plate 49and a doubler plate 112. Block 111 overhangs the edge of carriage shellplate 113 and engages a block 114 welded in a pocket of the carriageshell. The lower end of block 111 is tapered to faciliate installing andremoving lid plate 49.

Pump

A novelpump is contained in cable drum 4] to pressure a hydraulic systemfor operating drum brake 43 and skyline clamp 50 as shown in FIGS. 9 to15. The pump is carried by the stationary shaft 40 mounted in carriageside plates 35. The pump has five stationary cylinders 122 containingpistons 123 operated by a six lobed rotary cam ring 124. Cam ring 124 isbolted to tabs 125 in the drum. The space within the drum not occupiedby these parts fonns an oil reservoir 126. The drum rotates on bearings127 on shaft 40 equipped with suitable seals to retain the oil supply inthe reser- The object of this arrangement is to provide a birotationalpump that operates equally well in either direction of rotation andproduces high pressure oil efficiently at a low speed of drum rotation.This arrangement also provides a compact form of construction which doesnot require other valuable space for the pump and reservoir and providesmaximum protection for the pump. Conventional birotational pumps are notefficient at low speeds to produce a high pressure output. They requirea high ratio gear train in order to deliver enough oil at low speeds.Such a gear train requires space not available in a skyline carriage,the gear train is costly initially and would rotate the pump atdestructively high speeds if the turn of logs was accidentally dropped.

The construction of the present pump is such that accidental high speeddoes not damage the pump. The pistons do not draw in a full charge ofoil under an abnormal high speed condition. Each piston has a relativelysmall displacement but by operating the five pistons by six cam lobes anadequately large total displacement is obtained at low speeds. Thepistons make strokes per drum revolution. All the pistons are out ofphase with each other and a relatively even discharge flow results.Piston leakage is of no consequence because any leakage merely returnsto reservoir 126. Piston leakage is minimized by reason of the longbearing area between the piston and cylinder wall.

Referring now to FIG. 10, each piston 123 is urged outward by acompression spring 129 and is moved inward by a cam follower arm 130.Each arm 130 is pivotally mounted at 131 on a bracket 132 on astationary housing block 135 which may be a part of shaft 40. The outerends of arms 130 are equipped with cam follower rollers 136 which rideon the cam ring 124. Intermediate their ends, the arms 130 are equippedwith rollers 137 which engage the ends of pistons 123. This arrangementeliminates any side loading on the pistons.

Oil enters the pump from reservoir 126 through inlet screen 140 andinlet connection 141 to inlet manifold 142 in block 135. (FIG. 13). Atthe inner end of each cylinder 122 there is a combined inlet and outletvalve unit 143. This valve unit has an axial chamber 144 containing aninlet check valve 145 normally closed by a spring 146 as shown in FIG.12. An inlet port 147 communicates with inlet manifold 142 and acylinder port 148 communicates with cylinder 122. Thus, as piston 123moves outward, valve 145 opens to admit an inlet flow from manifold 142through ports 147 and 148 into the cylinder.

As piston 123 moves inward, the cylinder discharges through port 148,chamber 144 and a port 149 normally closed by outlet check valve 150.Check valve 150 is seated by a spring 151 in a radial chamber 152. Thefive chambers 152 discharge into a discharge manifold 153 in FIG. 11which communicates with a longitudinal discharge passageway 155extending toward one end of shaft 40.

A pressure relief valve 156 mounted in port 158 in FIG. 14 preventsexcessive pressure from developing in the pump discharge. A bypass line157 delivers the excess unused flow to a nozzle 160 directed into inlettube 161 in FIG. 9. This relief valve bypasses almost constantly and itsdischarge is used to supercharge inlet tube 161 and manifold 142. Thejet from nozzle 160 carries with it additional oil from reservoir 126.

A port in the outer end of pump discharge passageway 155 outside of drum41 connects with a hydraulic line 171 carrying pump pressure to themultiple valve unit V in FIGS. 2 and 19. This pressure is transmitted atall times through line 172 to hydraulic accumulator 173 and to skylineclamp retract cylinders 95. Valve unit V controls the application of oilpressure to brake cylinder 44 and also controls the application of oilpressure to a hydrostatic transformer 175 which supplies a higherpressure toskyline clamp cylinders 70. Return flow is conveyed fromvalve unit V through line 176 to a port 177 in the outer end ofa secondlongitudinal passageway 180 in shaft 40 as shown in FIGS.

9 and 15. This oil returns to cable drum reservoir 126 through port 181in the inner end of passageway 180.

As the volume of oil changes in accumulator 173, the volume changes incable drum reservoir 126. To prevent pressure or vacuum buildup inreservoir 126, breathing is provided through the stand pipe 183 shown inFIG. 14. Stand pipe 183 is screwed into a port 184 in the inner end of athird longitudinal passageway 185 in shaft 40. A port 186 in the outerend of passageway 185 is connected with a hydraulic line 187 toexpansion tank 190 in FIG. 2. The expansion tank is vented to atmospherethrough a port 191.

The ends of the various bore holes forming the oil manifolds andpassageways just described are closed by plugs 193.

Hydraulic System The hydraulic system is illustrated schematically inFIG. 18 in combination with the radio control system. The plurality ofskyline clamp cylinders is represented by the single cylinder 70 and theplurality of clamp retractor cylinders is represented by the singlecylinder 95. The control of these cylinders and brake cylinder 44involves primarily multiple valve unit V and hydrostatic transformer175. Valve unit V is associated with brake application solenoid valveSV1, brake release solenoid valve SV2, clamp application solenoid valveSV3 and clamp release solenoid valve SV4. These solenoid valves may beof the in-line type connected exter' nally to valve unit V or they maybe of the plug-in type which screw into ports in valve unit V and becomean integral part thereof. The solenoid valves are controlled by fourdifferent signals received by radio receiver R through its antenna 220.The radio receiver and solenoid valves are energized from a battery 221.

For a better understanding of the hydraulic system, reference is made toFIG. 19 showing the structural details of valve unit V and hydrostatictransformer 175. Oil from pump 120 flows through the previouslymentioned discharge line 171 and a check valve 222 into the main inletdistribution manifold chamber A in valve unit V. Pump pressure inmanifold A is communicated at all times through port 223 to clampretractor cylinder 95, through port 224 and line 172 to pressureaccumulator 173 and through port 225 and filter 226 to a port 227 insecondary distribution manifold chamber B. Thus, manifold B is alsounder pump pressure at all times.

Brake application solenoid valve SV1 is connected between a port 228 inmanifold B and port 229 in brake fluid manifold C. Brake cylinder 44 isconnected to a port 230 in manifold C. Thus, energization of solenoidvalve SV1 opens the valve and applies oil pressure to brake cylinder 44to tighten the brake 43 on brake drum 42 of the cable drum 41 in FIG. 2.

Brake 43 is released by energizing brake release solenoid valve SV2 toopen the valve. This valve is con nected between a port 231 in manifoldC and a port 232 in relief manifold chamber F. Manifold F dischargesthrough port 233 and the previously mentioned return line 176 to cabledrum reservoir 126.

The skyline clamp 50 in FIG. 2 is applied by energizing clampapplication solenoid valve SV3 to open the valve. This solenoid valve isconnected between port 238 in manifold B and a port 239 in pilot fluidmanifold D. The introduction of oil pressure into manifold D does twothings. First, it shifts piston valve 240 to the right to close anorifice 241 between working fluid manifold chamber E and relief manifoldchamber F since there is no opposition to the movement of piston 240.Second, it moves piston 242 to the right causing stern 243 to unseatcheck valve 245 from an orifice 246 between manifolds A and E,introducing oil pressure into manifold E.

Check valves 222 and 245 are normally seated by a common compressionspring 247. Piston 242 is considerably larger than orifice 246 so thatthe piston force applied through stern 243 exceeds the spring force plusfluid pressure force acting on check valve 245 in manifold A. Oilpressure in manifold E does not unseat piston valve 240 because of thesmall piston area exposed to pressure in manifold E after the valve hasclosed ori- Pressure in manifold E does not shift piston 242 back to theleft because the oil is locked in, in manifold D, and pressures are, ineffect, equal in manifolds A, E and D. Port 250 conveys the oil throughline 251 to port 252 in the low pressure end of hydrostatic transformer175. Skyline clamp cylinders 70 are connected to a port 253 in the highpressure end of the hydrostatic transformer, the operation of which willbe presently described.

The skyline clamp is released by energizing clamp release solenoid valveSV4 to open the valve. This valve is connected between port 255 in pilotfluid manifold D and port 256 in relief manifold F. This permitspressure in'manifold D to bleed off through manifold F to reservoir 126.Piston 242 is subjected to high pressure in manifold E across its entireface area while face area of piston 240 in manifold E is reduced by thearea of orifice 241. Therefore, the pressure drop in manifold D closescheck valve 245 first and then allows the pressure in manifold E to movepiston 240 away from orifice 241. This immediately relieves the pressurein manifold E, permitting oil to return from the low pressure end ofhydrostatic transformer 175 through line 251 to manifold E, thencethrough orifice 241 and chamber F to reservoir 126.

With the relief of fluid pressure from clamp cylinders 70, thecontinuously pressurized retractor cylinders 95 retract the movableclamp jaw 66. As the clamp jaw retracts, a considerable flow of oil fromclamp cylinders 70 is displaced through hydrostatic transformer 175 andline 251 to manifold E and continues until all the displaced oil isexhausted from cylinders 70. This action must be completed quickly toprevent sliding wear on the skyline.

Hydrostatic transformer 175 operates as an automatic pressureintensifier to raise the pressure in clamp cylinders 70 and conserveoil. Assuming a pressure of 3,000 psiintroduced into port 252, the clampcylinders 70 will be supplied with oil from port 253 at a pressure of10,000 psi. Hydrostatic transformer 175 accomplishes this without theuse of heavy springs, external valves and complicated pipingarrangements.

Piston 270 has a large end movable in a large cylinder 271 and a smallend movable in a small cylinder 272. Thus, the large end of the pistonoperates in a chamber G in cylinder 271 and the small end of the pistonoperates in a chamber H in cylinder 272. Piston 270 contains a centralpassageway 273 equipped with a check valve 275 normally seated by aspring 276. An oil line 277 having a check valve 278 connects port 279in chamber G with port 280 in manifold F of the valve unit V. An oilline 281 having a restrictor 282 connects a port 283 in chamber G withport 284 in manifold F. When piston 270 is fully retracted, check valve275 is unseated by a fixed rod 274, not: shown.

Check valve 278 and restrictor 282 control the oil in chamber G. Thechamber G may fill rapidly with oil from manifold F when piston 271]) isretracting upward but outflow when the piston is moving downward isrestricted at 282. The pressure in chamber G is approximatelyatmospheric pressure at all times except for a brief period while clampcylinders are being actuated.

When manifold E in valve unit V is pressurized by the energization ofsolenoid valve 3V3 as previously described, oil enters port 252 ofhydrostatic transformer 175, thence flowing through passageway 273 ofretracted piston 270 and chamber H into clamp cylinders 70. Thus, themovement of the pistons 71 in cylinders 70 necessary to close themovable clamp jaw 66 is produced by oil under system pressure flowingdirectly from working fluid manifold E without any pressureintensification. During this interval, piston 270 is restrained frommoving because of the resistance to the outflow of oil from chamber Gimposed by restrictor 282.

When pistons 71 under system pressure reach their limit of movement inclamped position, the oil flow through passageway 273 ceases and thedifference in end areas on the upper and lower ends of piston 270 causesthe piston to move downward until check valve 275 closes passageway 273.The piston comes to rest in an equilibrium position when the product ofthe oil pressure and piston area becomes equal on the large upper endand small lower end of the piston. This re sults in a high pressure inchamber H and cylinders 70 to exert a powerful clamping force againstthe movable clamp jaw 66.

It is to be emphasized that clamping is accomplished with systempressure first. Then, and only then, does pressure intensification takeplace. This conserves oil tremendously since all movement of the clampjaw is taken up with system pressure first. If chamber H on to clampcylinder 70 were a so-called closed circuit, then piston displacement inchamber H would have to be larger and displacement in cylinder 271 mustthen be approximately 3 /2 times that of chamber H. This would requirean excessive volume of oil and a hydrostatic transformer of excessivelylarge size.

When the pressure in manifold E is reduced to relief pressure by theopening of piston valve 240 in response to energization of solenoidvalve SV4 as described above, oil flows out of the upper end of cylinder271 through port 252, line 251, manifold E, orifice 241 and manifold Fto reservoir. This allows piston 270 to move upward, gradually reducingthe intensified pressure in Valve unit V has three primary features andadvantages. First, it provides a leak-proof system for controlling theoil used for the skyline clamp. Second, it provides a compact andrelatively simple manifold assembly for internally connecting many ofthe hydraulic lines and fittings which would otherwise require acomplicated and cumbersome array of plumbing. Third, this valve unitkeeps the high pressure line open to maintain pressure on the clampcylinders until the action is reversed without having to keep the clampapplication solenoid energized, thereby conserving battery power.Likewise, in the retracted position of the clamp, it keeps the hydrauliclines open to the reservoir until the action is reversed without acontinuous drain on the batteries. Further, this valve unit preventscross flow during the valving cycle. High pressure oil cannot flow intothe low pressure line during the operation of the valving cycle.

If the system pressure is below normal for some reason when the skylineclamp is applied, as for example say 2,500 psi, this would produce areduced clamp cylinder pressure of about 8,700 psi. But since valve unitV holds the pressure line open to the hydrostatic transformer, anypressure build-up in the system resulting from cable drum rotation isimmediately transmitted to the clamp cylinders restoring their normaloperating pressure. Each application of the skyline clamp causes apressure drop in the system and subsequent drum rotation restores normalpressure. In normal use the cable drum is operated immediately aftereach application of the clamp. For example, merely lowering the hoistingline to pick up a load insures full clamp cylinder pressure when it isneeded most, during the lifting of the load.

The nature of the carriage is such that only a limited amount of oil isavailable to operate the skyline clamp and cable drum brake. Therefore,the hydraulic system must be such that no oil can be lost. The clampmust not be subject to premature release because of leakage in thehydraulic system. The brake must not be subject to premature releaseregardless of how long the turn of logs hangs suspended in the air.Extreme danger would result if the brake or clamp were to releaseunexpectedly.

Since the pressures in manifolds D and E are substantially equal in boththe applied and released positions of the clamp, leakage through or bypistons 240 and 242 is of no consequence. The construction of the foursolenoid valves is such that in the deenergized positions, highpressures on the upstream sides of the valves tend to hold them tightlyclosed without leakage. The radio receiver R includes a timing device tohold the solenoid valves energized for a period of one second and thendeenergize them. During this time interval the brake or clamp is fullyapplied or fully released without continued drain on the battery.

Valve unit V uses a minimum of oil for the pilot circuit in manifold Dbecause pistons 240 and 242 move only enough to equalize pressuresin'manifolds D and E. After these pressures are equal, the pistons donot displace additional oil. In the clamp release function, again thesepistons move only enough to equalize pressures in manifolds D and E.Thus, in both phases of the clamp operation there is no wasted oil inthe pilot circuit operation.

The present hydraulic system is to be distinguished from systemscontrolled by conventional pilot-actuated spool valves wherein a spoolis shifted to control the main oil flow. Conventional spools necessarilyentail tremendous leakage regardless of the excellence of theirmanufacture and regardless of the close tolerances obtained. The presentsystem will hold its pressure for a period of weeks while standing idleand is then ready to resume operation without first pumping up the oilpressure.

The present hydraulic system also includes an additional and uniquesafety feature. Some yarders do not have enough power in their skylinedrum to pick up the carriage and a turn of logs if suspended at theskyline midway point, making it necessary to hold the skyline drum witha dog if the yarder drum brake is not adequate to hold the drum fromturning. Operating with such a yarder presents a serious hazard if thebattery wire should break or the radio fail while the carriage issupporting a turn of logs near a midway position on the skyline. Thepresent system is arranged to forestall serious trouble in such event.

In FIG. 19 a ring of small copper tubing T is connected to a port 265 inpilot fluid manifold chamber D of the valve unit V. As shown in FIGS. 2and 3, the ring T is tucked into the inside corner of a ring 266 ofsteel rod which is welded to the outside of carriage side plate 35.Shooting into this target area with a small caliber rifle will splatterthe bullet into the copper tube, rupturing it and releasing the pressurefrom manifold D thereby releasing the skyline clamp as is done in theusual manner. The release of pressure from manifold D does not releasethe cable drum brake 43 whereby the carriage with its turn of logs maystill be moved along the skyline by the yarder winch drums 21 and 22.

Another feature of great importance is that it is impossible to applythe skyline clamp only partly on or partly off, which could allow it toslide on the skyline and cause destructive wear on the skyline cable. Aspreviously mentioned, the radio receiver includes a time delay devicethat prevents deenergization of any energized solenoid valve for aperiod of one second. During this time interval, manifold D is eitherpressurized or de-pressurized, as the case may be, and the skyline clampis either applied fully on or is completely released. It is impossibleto apply the clamp only partly on or to release it only partly. It is atall times either fully applied or fully released.

In FIG. 20 the valve unit V is a solenoid controlled three-way valvewhich is a modification of the valve unit V in FIG. 19, correspondingparts being identified by the same reference numerals. In this case, thesingle acting cylinder 270 is pressurized by energizing solenoid valveSVS which performs the same function as SV3 in FIG. 19. Cylinder 270 isrelieved of pressure by energizing solenoid valve SV6 which performs thesame function as SV4 in FIG. 19. In FIG. 20 manifold chambers A D,, Eand F correspond to manifold chambers A, D, E and F, respectively, inFIG. 19. With only small solenoid valves SV5 and SV6 to change thepressure in pilot fluid manifold chamber D very large volumes of oil canbe controlled in working fluid manifold chamber E without leakagethrough the valve. The operation is not affected by dirty oil becausepistons 240 and 242 are acted upon by the full oil system pressure whichis adequate to move the pistons regardless of the presence of dirt inthe oil. However, a filter as well as pressure accumulator may beemployed with the valve unit V,, if desired. Valve unit V is of generalapplication to hydraulic systems for various purposes where the majorfeatures of valve unit V are of advantage.

Having now described our invention and in what manner the same may beused, what we claim as new and desire to protect by Letters Patent is:

1. In a skyline logging carriage, a skyline clamp comprising astationary jaw and a movable jaw, means holding a plurality of hydraulicclamp cylinders loosely in position at intervals along said movable jawto apply direct thrust against said movable jaw, and a pair ofabutmentblocks on the carriage engageable with opposite ends of said movable jawto resist end thrust on said aw.

2. A skyline logging carriage as defined in claim 1, including aplurality of hydraulic cylinders arranged to retract said movable jaw.

3. A skyline logging carriage as defined in claim 1, said holding meansalso holding said movable jaw loosely in operative position fortransverse movement toward and away from the skyline and for lengthwisemovement against one or the other of said abutment blocks, said holdingmeans-being releasable and said movable jaw being removable from thecarriage when said holding means is released.

4. A skyline logging carriage as defined in claim 3, said holding meanscomprising a lid plate on the carriage having rectangular holes narrowerthan said clamp cylinders supporting said cylinders in horizontalposition, said lid plate supporting said movable jaw for said transverseand lengthwise movements, and a hinged overarm assembly overlying saidcylinders and movable jaw holding said cylinders and movable jaw looselyin operative positions.

5. A skyline logging carriage as defined in claim 1' including ahydraulic pressure system in the carriage, and a hydrostatic transformerconnected with said pressure system and said clamp cylinders, saidhydrostatic transfomier operating said clamp cylinders at said systempressure in moving said movable jaw from a retracted to a clampedposition and then operating as a pressure intensifier to increase thehydraulic pressure in the clamp cylinders to a pressure higher than saidsystem pressure.

6. A skyline logging carriage as defined in claim 5 including retractorcylinders acting on said movable jaw at all times under said systempressure, said retractor cylinders being effective to retract saidmovable jaw when said clamp cylinders are not energized.

1. In a skyline logging carriage, a skyline clamp comprising astationary jaw and a movable jaw, means holding a plurality of hydraulicclamp cylinders loosely in position at intervals along said movable jawto apply direct thrust against said movable jaw, and a pair of abutmentblocks on the carriage engageable with opposite ends of said movable jawto resist end thrust on said jaw.
 2. A skyline logging carriage asdefined in claim 1, including a plurality of hydraulic cylindersarranged to retract said movable jaw.
 3. A skyline logging carriage asdefined in claim 1, said holding means also holding said movable jawloosely in operative position for transverse movement toward and awayfrom the skyline and for lengthwise movement against one or the other ofsaid abutment blocks, said holding means being releasable and saidmovable jaw being removable from the carriage when said holding means isreleased.
 4. A skyline logging carriage as defined in claim 3, saidholding means comprising a lid plate on the carriage having rectangularholes narrower than said clamp cylinders supporting said cylinders inhorizontal position, said lid plate supporting said movable jaw for saidtransverse and lengthwise movements, and a hinged overarm assemblyoverlying said cylinders and movable jaw holding said cylinders andmovable jaw loosely in operative positions.
 5. A skyline loggingcarriage as defined in claim 1 including a hydraulic pressure system inthe carriage, and a hydrostatic transformer connected with said pressuresystem and said clamp cylinders, said hydrostatic transformer operatingsaid clamp cylinders at said system pressure in moving said movable jawfrom a retracted to a clamped position and then operating as a pressureintensifier to increase the hydraulic pressure in the clamp cylinders toa pressure higher than said system pressure.
 6. A skyline loggingcarriage as defined in claim 5 including retractor cylinders acting onsaid movable jaw at all times under said system pressure, said retractorcylinders being effective to retract said movable jaw when said clampcylinders are not energized.